Trinseo S.A. (NYSE: TSE) (the “Company”), a global materials solutions provider and manufacturer of plastics, latex binders and synthetic rubber, today announced that Bain Capital Everest Manager Holding SCA (the “Selling Shareholder”) has agreed to sell 8,000,000 ordinary shares pursuant to the Company’s shelf registration statement filed with the Securities and Exchange Commission (the “SEC”). The Selling Shareholder will receive all of the net proceeds from this offering. No shares are being sold by the Company. Morgan Stanley & Co. LLC and Jefferies LLC will act as book-running managers for the offering.

A shelf registration statement (including a prospectus) relating to the offering of ordinary shares was filed with the SEC on March 15, 2016 and became effective on March 18, 2016. Before you invest, you should read the prospectus included in that registration statement and the documents incorporated by reference in that registration statement as well as the prospectus supplement related to this offering. You may obtain these documents for free by visiting EDGAR on the SEC website at www.sec.gov. When available, copies of the prospectus supplement and accompanying prospectus related to the offering may also be obtained by contacting Morgan Stanley & Co. LLC, Attn: Prospectus Department, 180 Varick Street, New York, New York 10014 or Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 2nd Floor, New York, NY 10022, telephone: 1-877-821-7388 or e-mail: Prospectus_Department@Jefferies.com

The offering of these securities will be made only by means of a prospectus supplement and the accompanying prospectus.

This release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or other jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction. Any offer to buy the securities may be withdrawn or revoked, without obligation or commitment of any kind, at any time prior to notice of its acceptance given after the effective date of the shelf registration statement.

About Trinseo

Trinseo (NYSE: TSE) is a global materials solutions provider and manufacturer of plastics, latex binders, and synthetic rubber. We are focused on delivering innovative and sustainable solution to help our customers create products that touch lives every day - products that are intrinsic to how we live our lives - across a wide range of end-markets, including automotive, consumer electronics, appliances, medical devices, lighting, electrical, carpet, paper and board, building and construction, and tires. Trinseo had approximately $4.0 billion in revenue in 2015, with 18 manufacturing sites around the world, and more than 2,200 employees.

Note on Forward-Looking Statements

This release may contain “forward-looking statements” within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. Words such as “expect,” “estimate,” “project,” “budget,” “forecast,” “anticipate,” “intend,” “plan,” “may,” “will,” “could,” “should,” “believes,” “predicts,” “potential,” “continue,” and similar expressions are intended to identify such forward-looking statements. By their nature, forward-looking statements involve risks and uncertainties because they relate to events and depend on circumstances that may or may not occur in the future, including risks and uncertainties relating to the consummation of the proposed offering by the Selling Shareholder and the repurchase by the Company and the risks identified, or incorporated by reference, in the prospectus supplement or accompanying prospectus. As a result of the foregoing considerations, you are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release. All forward-looking statements are qualified in their entirety by this cautionary statement. The Company undertakes no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.